Radio navigation system



Aug. 26, 19 2 c. E. HASTINGS 2,608,685

RADIO NAVIGATION SYSTEM Filed Oct. 11, 1950 2 sm Ts-sHEET 1 ROUGH POSITION POSITION H I i/A35 F/LTEPS METERS 30 INVENTOR.

BY WWI 1%) ATTORNEYS.

2 SHEETS-SHEET C. E. HASTINGS RADIO NAVIGATION SYSTEM Aug. 26, 1952 Filed 001:. 11, 1950 m E N m w A INVENTOR'.

Ch azJe-s Eaiasw s, W Y

Patented Aug. 26, 1952 mimo NAVIGATION SYSTEM Charles ErHastings, Hampton, Va., assignor to Hastings Instrument Company, Inc., Hampton,

I Va., a corp'oration of Virginia Application October 11, 1950, Serial No. 189,633

Thisinvention relates vnavigation system and method operable on the. principle of phase comparisonof beat frequenciestbetween the signals of pairs of transmitters, as detected at spaced points.

It is an object of the present invention to provide a navigation system and method capable of determining position with, anextremely high degree of accuracy, and without ambiguity, 1

It is a further object of they inventiontoprovideanaviga'tion system; and method; capable of determining positionzsubstantially instantaneous- 1y, without regardtoprevious knowledge of position or tracking. H

1A furthertobject is to provide anavigation system': and'method employingstandard radi communication units." z

Another object of the invention is to provide an unsaturable navigation system and';method, which may be used simultaneouslyby any number of mobile objects-.todetermine their: position.: i

Further part pointed out hereinafter inthis' specification and the appended claims. t

The invention and the novel features thereof may best be made clearifrom the following dei scription and the accompanying drawings in which: i

Figure Iis a block diagram illustrating an enemplary embodiment of the invention, showing the basic elements thereof, and V, v

Figure .2 is. a diagram corresponding generally to Figure l, illustrating -.one mode of operation of thesystem. :1

Referring to thefidrawingsrinblii ire :1 is shown an exemplary, embodiment of ,the invention, ineluding a group of fixed transmitters gill, Hand I4, the term fixed, beingemployed toconnote known, position,v 1 The transmitters m p er on any assigned frequency a, frequencyessign of ,each group, it-will berecogniz ed thatthis is not ssential-1 The tw u s 7 of transm are objects will be obvious and in differently positionedrelative to each other, and

preferably angularly positioned relative, to each other, as shown. As in the case of the first group,

the transmitters of the second group are adapted to transmit at differentfrequencies. Transmit.- ter [6, for examplamay transmit at a frequency 725 cycles above that of transmitterldi, .or I725, and transmitter 20 may transmit at a frequency 450 cycles above the frequency of'transmitter i4, orfiso.

Further essential elements of the invention include a stationary receiver 20, and a mobile receiver 22, which latter unit may be carried onra ship, aircraft or other mobileobject. [The mobile receiver, it will be understod, is merely a. receiver of unknown position, and need not necessarily be moving, nor even movable. If the system is to be employed over water, th'etransmitters and the fixed receiver may conveniently be arranged along a shore line 24, as shown Receiver 20 may be located at any convenientposition where it may remain stationary with respect to the previously mentioned transmitters.

The receivers 20 and 22 are adaptedtoreceive the transmissions of thevarious transmitters and I detect the beat frequencies therebetween, and the receiverswill obviouslydetectthesame beat ire quencies whereverl locatedl. However, it will be recognized that the "phase oflltlie l detectedi beat 6 frequency signals'will vary with the position of ,the'receiver. By measuringTthe phase difference between like beatfrequency signals detected v by two spaced-apart receivers thatis by measuring the difference in phase between the, beat frequenv f h ns iss n t e Sam t a sm t r. pair as detected at ,different positions, a hypere boliciline of position; of themobile receiver relative to that transmitter-pairmaybe determined. The greater the spacingbetweenthetransmitters, the greater will be the. accuracy with which i the to a conventional phaselmeter adaptedto indicate'the phase difference therebetween. Onereceiver being ffixed, the phase difference-so deter- -mined will vary with difference in distance between the mobiler eceiver' on the one hand; and

each of thetransmitters on the other. so long as the differenceindistancebetween the mobile signals will not vary; 1 Accordingly,itifollowsjthat if the mobile receiveralong hyperbolic,

3 path having the transmitters as focal points, no change in phase difference will be efiected, while if the mobile receiver moves laterally relative to V such a path, a corresponding change in phase difference will take place. 7

Accordingly, the phase difference indicated by the phase meter will be indicative fof the position of the mobile receiver with respect to a family of hyperbolas having the transmitters as focal points. Using conventional transmission the rough position of the mobile transmitter.

I frequencies and a spacing betweentran'smitters consonant with great accuracythe distance between transmitters 'willbe reatf relative'to the; wave length of transmission, and the family of; hyperbolas will constitute a plura lity of sectors or lanes, each defined by hyperbolic lines spaced one-half wave length apart where they intersect a straight base line drawn between the transmittersr Traverse of ,alane so defined by thamobile receiver am change the dififerential change in phase diifere'rieei phas'eiiiete it follows that if the zero post? tith;bf'th'-phas'iiieter is adjusted to correspond tt posit th tithe biieret'eivet .oh onse the ane-d'enhi li phase meter reading will directly indicate a line or position within larie;

although .it will not identify thelane wherein the r'ceivr'lies H If We trahsmitter's-iare located at stations distance etween the receiver; and the transmit-'- ters th wave, iengt therebyv effecting a 360 indicated" by a" thejwave, length or transmission thereof, the" prtbiefiihi lanideiitification does not aris'e,sin 'ce' the entire jpossi bleraiig'e of, movement. of the mobilei ece'iver results in atha'ngm phase fdif; ferencexi t exceeding one cycle, or not eii'cje'eding scores recqrued by'theepiiase met r. In this hyperbolicljline' o'f po t t relative t the ce'ivers which may berea'dily' and directl'y estab lished, V The line of position 'soestablishejd, isflinsum "ently aocurat ridicat'eposition withpre- .case, then, the phasemeter reading indicates a cisionbutjt is an utst'andin feature oi'the' es nt-memen o 67m h? W fim te sis' spaced *to determine the rtii position of the j p I V j fbvia thereb'y'the problenr 01' lane, identification 1 Re e r n to re ief-2 a m n on of mobileireceiver flias show 7 pairs" Ill- 2" and I-6' l 8- are spaced apart a disif the transmitter viously established indicating the lines" of land demarcation relative-to the transmitters: anda plurality of intermediate lines of position in each tame-hot zreeedifihalfth e wave-length" elf-the m s ions thereof; it 'will ts readily understood 7 that 'lir'ie's' 'o f p'os'ition of the mobile receiver 22 i -may zbe' readily established with;'respect to the transmitter 'pairs' H1 42 thaws-4a,: That-' is",-- theiphase difierence between the beat -fr'elquency of-the' transmitter qpair 10+I-2 as detected by re-# ceivers 20an'd 22 will be-indicative of the-posi tion of receiver22 with respect to a-family ofhyperbolic lines illustrated in the drawings as dotted lines a,x.these1 lines having receivers i0 and l2vv as focal points. Simi1arly, the phase difference between the beat frequency ofxtransmitters l6 and as ,detectedbylreceivers 20 and 2-2 will indicate the position of. receiver 221'61-5 ative to a; similar Iamily of hyperbolic linesil-t.

lustrated asqdotted lines 27, these lineshaving transmitters l6, and l8 as focal points, vThe transmitters .beingiixed in position,theiamilies of hyperbolic lines may be previously established and identified with phase meter readings, and employed as an overlay with amapbrthearea; whereby the phasemfeterlreadings i ay' be easily 1 5 converted into lines or position,"or the data de- "Employing next the transmitter pairs Ill-l4 and Id- 118, and determining the phase differ- .ence'between, the autio beats thereof as detected bYthe receivers---a, fine position of the mobile transmitter "may be determined (with much greater accuracy: Iii the example shown, trans- ,mitters i0 "and--lil .are spaced apart three wave lengths,, whereby six lanes of position are establishediherebetween, the. lanes being separated by imaginary hyperbolic lines A, having transmitters I 0 and Has focal points and separated.

' one-half wave l'ength where theyyintersect" the:

base line extending-between Tth transmitters. Accordingly, movement-'fofgthe mobile receiver from one line A to the next on either side will. effect a ohange of 360?;in the phase difference between the beatffequen'ci'es ofthetransn iise sions of the transmitter: pair-10;; aside'tected by the receivers and: will'efiect a corresponding complete ievolu'tidn (ifthe imam-meter. J If; the

phase meter be zeroed toicorrespondrto the lines of; lane demarcation, the; meteriwill indicate di;-; rectly hyperbolic :li'nesiiofr position intermediate the lines of lane demarcation with greatzaceuracyz Similarly, transmitters 'l 4 and 21183 are ;J'spaced apart three wave lengths, establishing six; lanes of position there'between, separatediby'imag-inary 1 hyperbolic-lines.B.:...; t-

A's in-the previous; caseyatplot'may. be pre-.-

lane. corresponding-11:6 :p-hasemeter readings. Employing; this. plot :as an oveflam. the rough position of the receiver as established by transmitter pairs 1 ll-e-l 2 and. l 6-18 will immediately identify the lane. inwhich the receivert'i's; p081? tioned.. The lane; being thus identified, the phase difference between the beat signals de'-" tected by receiver's'20- and 22 may be utilized with the plot to establish the linear position of the receiver with great 'acburacyi lSimi-larly, em ploying transmittersaittiand:18; another line of position i of-receiver 22ore1ative to these: trans mitters may be determined with corresptm'dii' ig accuracy. the problem oflaneidentification being ag'ain obviated by he rougltipdsi-tion-h'f the re ceiver previeusiy et'ermined ZTh'e intersection" Of-fth lin'es of. position 'deriv'ed i from the beat frequencies of was; the

ant e" et't emotuete eiveh the t a y} particular 'etringoratmi her need the groups be disposed at-sit right afile of any 6 angle relative to eaehtthe -it 'ab'e" en hp o w h -'P"31%endiiit!r is'g ih ahartarthstaiiatithgros trample, the-only accurately est'ablisii the fine" cables. cies "may be amplified, desirably by matched requirement-is that the rough position transmitters be so oriented that the hyperbolic linesrepresenting 0 and 360 are wide enough to circumscribe the entire water area.

The position determination as outlined above may be made within a very short time, of the order of a few seconds or less. In the system of Figure 1, for example, the signals detected by receiver 20 may be relayed by a reference transmitter 26 to a receiver 28, also located on the mobile object. It will be evident that in other applications, the beat frequencies detected by the fixed receiver may be relayed to a common position by other means, such as telephone lines or At the mobile object, the beat frequenamplifiers of a constant output type, and the output of the amplifiers fed to a plurality of filters 30. As shown in the figure, the signals detected by each receiver at the mobile position are fed to four different filters, adapted, in the, assumed example, to pass beat frequencies of 150, 275 350 and 450 cycles, respectively. The filter pairs are desirably matched, the 150 cycle filters being matched to each other and so forth. So separated, the like beat frequencies passed by the filter pairs are supplied to conventional phase meters 32. It will be apparent that the 150 cycle beat frequencies passed by one filter pair will effect a reading on the phase meter to which these signals are fed indicating a rough line of position of the mobile object relative to the transmitter pair l0-l2. 'Similary, the 275 cycle signals fed to another phase meter 32 will indicate the rough line of position of the mobile object with respect to the transmitter pair 16-48. The 350 cycle signals fed to a third phase meter will indicate the fine line of position of the mobile object with respect to transmitter pair Iii-l4 and the 450 cycle signals will indicate a fine line of position of the mobile object relative to transmitter pair l4l8. In this manner, on a proper plot of the area previously established relative to the fixed position of the transmitters, or by computer or other means, the phase meter indications will establish both rough and fine position of the mobile object. The rough position readings will immediately establish the lane position of the mobile receiver relative to transmitter pairs ill-44 and l4-l8, and the readings of the fine position phase meters will indicate lines of position within those lanes by which the position of the receiver may be established with great accuracy.

The system described will operate consistently with accuracies of one part in 5,000 or one foot, whichever is greater, at ranges of up to a hundred and fifty miles during daylight hours and seventy-five miles at night. Under excellent propagation conditions, daytime operation may be satisfactory at ranges in excess of five hundred miles. If accuracy of the highest order is required, further transmitter pairs may be employed, spaced apart greater distances than the receiver pairs l0l4 and l4--l8, with additional filters and phase meters on the mobile object. Obviously, the greater the spacing between transmitters the higher the accuracy, and since lane ambiguity is obviated by the present invention, the greatest accuracy is possible.

In order to reduce the mobile equipment to a minimum, conventional frequency selective filters 34 may be employed on the mobile object, together with switching means 36, as illustrated in Figure 2. In this case, only a single phase meter 32 is required. While employing less equipment, this variation requires slightly more time to indicate position, since the fouror more required phase meter readings must be obtained successively,.rather than simultaneously, and if the mobile object is moving rapidly accuracy will be somewhat reduced.

While the foregoing relates to a two dimensional navigation system and method, it will be apparent that the system may be extended to three dimensions by arranging transmitter pairs vertically or angularly relative to the ground. The system is extremely flexible, and may readily be expanded into a continuous chain. An additional station maybe established merely by a single additional CW transmitter. The transmitters may be hermetically sealed and equipped with small whip antennas, and readily attached to existing power line or telegraph poles. The resulting flexibility of transmitter location makes it possible to establish lines of position having good intersections in any area in a chain of stations. Some care must be exercised in selecting transmitter frequencies, to avoid undesirable harmonics and sub-harmonics. The exemplary frequencies listed above are entirely suitable, and further frequencies for additional stations may be readily determined.

It'will be recognizedthat the system. requires but a single primary frequency, and one additional frequency for the reference transmitter. Effects of frequency drift inherently cancel out. The system may operate continuously, no synchronizing methods being required, and may be used simultaneously by an unlimited number of mobile objects, each receiving its own position data.

It will thus be seen that there has been provided by this invention a system and method in which the various objects hereinbefore set forth, together with many practical advantages, are successfully achieved. As various possible embodiments may be made of the several. features of the above invention, all without departing from the scope thereof, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative, and not in a limiting sense.

I claim:

1. Apparatus of the class described comprising a plurality of transmitters adapted to transmit at different frequencies, one pair of said transmitters being spaced apart a distance not exceeding one-half the wave length of the emissions thereof and another pair being spaced apart a greater distance, two spaced receivers each adapted to detect the beat frequencies between the emissions of said transmitter pairs, and means for indicating the difference in phase between the beat frequencies detected by said receivers.

2. Apparatus of the class described comprising a plurality of transmitters adapted to transmit at different frequencies, one pair of said transmitters being spaced apart a distance not exceeding one-half the wave length of the emissions thereof and another pair being spaced apart a greater distance, a mobile receiver and a fixed receiver each adapted to detect the beat frequencies between the emissions of said transmitter pairs, and means associated with said mobile receiver for indicating the difference in phase between the beat frequencies detected by said receivers.

3. Apparatus of the. class: described comprising a plurality of fixed transmitters adapted to transmit. at frequencies differing by audio notes, one pair of said transmitters being spaced apart a distance not exceeding one-half the wave length of the emissions thereof and another pair being spaced apart a greater distance, a mobile. receiver and a fixed receiver each adapted to detect the beat frequencies between the emissions of said. transmitter pairs, and means associated with said mobile receiver for: indicating the difference in phase between the beat frequencies detected by said receivers. 4. Apparatus. of the class described comprising a plurality of fixed transmitters adapted to transmit at frequencies differing by audio notes, one pair of said. transmitters being spaced apart a distance not exceeding one-half the wave length of the emissions thereof and another pair being spaced apart a greater distance, a mobile receiver and. a fixed receiver each adapted to detect the beat frequencies between the emissions of said transmitter pairs, means for relaying the beat frequencies. detected by said. fixed receiver to the position of said mobile receiver, and. means associated with said mobile receiver for indicating the difference in phase between like beat frequencies detected. by said receivers.

5. Apparatus of the class described comprising three fixed transmitters adapted to transmit: at frequencies difiering by audionotes, the second of said transmitters being spaced from the first a distance not exceeding one-half the wave length of the emissions thereof and the. third of. said transmitters being spaced from the first a greater distance, a mobile receiver and a fixed receiver each adapted to detectthe beat frequencies between the emissions of said transmitters, and means for relaying the beat frequencies detected by said fixed receiver to the position of saidmobile receiver.

6. Apparatus of the class described comprising a first group of transmitters and a second group 7 of transmitters, said transmitters being adapted to transmit at different frequencies, one pair of transmitters of each group being spaced apart a distance not exceeding one-half the wave length of the emissions thereof and another pair of transmitters of each group being spaced apart a greater distance, two spaced receivers each adapted to detect the beat frequencies between the emissions of said transmitters, and means for indicating the difference in phase between. like beat frequencies as detected by said receivers.

7. Apparatus of the class described comprising a first group of fixed transmitters and a second group of fixed transmitters, said transmitters being adapted to transmit atdifferent frequencies, one pair of transmitters of each group being spaced apart a distance not exceeding one-half. the wave length of the emissions thereof and another pair of transmitters of each group being spaced apart a greater distance, a mobile receiver and. a fixed receiver each adapted to detect the beat frequencies between the emissions of said transmitters, and means for indicating, the difference in phase between like beat frequencies as detected by said receivers.

8. Apparatus of the class described. comprising a first group of fixed transmitters and a second group of fixed transmitters, said transmitters being adapted: to transmit at frequencies differing by audio notes, said groups of transmitters being difierently positioned relative to each other, one pair of transmitters of each group being spaced apart a distance not exceeding one-half thewave length of the emissions thereof and another pair of transmitters of each group being spaced apart a greater distance, a mobile receiver and a fixed 7 receiver each adapted to detect the beat frequencies between the emissions of said trans:

mitters, means for relaying the beat frequencies one pair of transmitters of. each group bein spaced apart a distance notv exceeding one-half the Wave length. of the emissions thereof and another pair of transmitters of each group being spacedapart a greater distance, a mobile receiver and a fixed receiver each. adapted to detect the beat frequencies between the emissions of said transmitters, means for relaying the beat frequencies. detected by said fixed receiver to the position of said mobile receiver, filter means associated with said mobile receiver adapted to pass like beat frequencies as detected by said receivers, and means associated, with said filter means for indicating the difference in phase between like beat frequencies passed thereby.

10. A position determining system comprising, a plurality of transmitters tuned to transmit at different frequencies, one pair of said transmitters being spaced apart a first distance, another pair of said transmitters being spaced apart a distance considerably greater than the said first distance, a mobilereceiver unit and a stationary receiver unit each adapted to detect the beat frequencies between. the emissions of the transmitters of each of the said transmitter pairs, means for indicating the diiference in phase between the beat frequencies of the said one pair of transmitters as detected by the mobile and stationary receiver units, means forindicating the difference in phase between thebeatfrequencies of the said other pair of transmitters asdetected by themobile and stationary receiver units, the first distance being sufficiently limited so that the phase relationship of the beat frequencies of the one pair of transmitters provides a position without ambiguity over the possible range of movement of the mobile receiver, whereby the indicated phase relationship of the beat frequencies of the second pair of transmitters may provide a position without ambiguity.

CHARLES E. HASTINGS.

REFERENCES CITED The following references are of record in the file .of this. patent:

UNITED STATES PATENTS 2,551,604 Jacobson May 8, 1951 

